POS0711 DEVELOPMENT OF THE TAKAYASU’S ARTERITIS INTEGRATED DISEASE ACTIVITY INDEX
Authors: C. Marvisi, E. C. Bolek, M. Ahlman, H. Alessi, E. Galli, C. Ricordi, F. Muratore, S. Kaymaz Tahra, F. Alibaz-Oner, S. Özgüven, P. A. Merkel, C. Salvarani, H. Direskeneli, K. A. Quinn, P. Grayson
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Disease activity indices that accurately assess inflammation in Takayasu's arteritis (TAK) are needed <sup>[1]</sup>. While clinical assessment is often considered the gold standard, determining if a symptom represents active vasculitis or damage can be challenging in TAK. FDG-PET can directly assess vascular inflammation but specificity of imaging findings, especially in absence of corresponding clinical symptoms, is questionable. <h3>Objectives</h3> The aim was to develop an index to assess disease activity in TAK called TAK Integrated Disease Activity Index (TAIDAI). <h3>Methods</h3> Clinical symptoms associated to TAK were derived from a comprehensive literature review <sup>[2]</sup>. TAIDAI was assessed in an observational cohort with a stepwise approach. All the symptoms present within 7 days of clinical evaluation were recorded by two clinicians, without determining whether the symptom reflected active disease or damage. Physician global assessment (PhGA) (scale 0-10) and certainty of the assessment (certain vs uncertain) were collected for every visit. Each patient underwent FDG-PET 24 hours after the clinical assessment. Active vasculitis, defined as arterial FDG uptake &gt; liver, was recorded in specific arterial territories and quantified using the PET Vascular Activity Score (PETVAS) <sup>[3]</sup>. To score TAIDAI, clinical symptoms are paired with specific arterial territories and only scored if there is active vasculitis by FDG-PET in a corresponding arterial territory. Constitutional symptoms are scored only if CRP ≥10mg/L or ESR≥40mm/hour. To determine content validity, correlations were performed between PhGA, patient-reported global assessment (PtGA, 0-10 scale), ESR, CRP, PETVAS, and TAIDAI. To determine criterion validity, performance characteristics of TAIDAI were calculated relative to clinical assessment, restricted to cases of assessment certainty. To determine responsiveness, TAIDAI scores were assessed longitudinally in patients initiated on tumor necrosis factor inhibitors (TNFi) or tocilizumab (TCZ). Complete response was defined as resolution of all symptoms of active vasculitis plus a daily prednisone dose not exceeding &gt;50% of the pre-treatment visit. <h3>Results</h3> 17 clinical symptoms were identified for inclusion in the index. TAIDAI was calculated for 96 patients over 204 visits. Clinically active disease was present in 62 (30%) visits, with uncertainty of assessment in 82 (40%) visits. Inter-rater agreement for PhGA was poor (45%). At baseline, median TAIDAI was 1 (range 0-9), and 48 (50%) patients had a TAIDAI of 0. TAIDAI &gt; 0 defined active disease with 96% sensitivity and 77% specificity compared to clinical assessment. TAIDAI score correlated most strongly with all other assessments (Table 1). Complete response was observed in 15/20 patients treated with TNFi and 8/11 patients treated with TCZ. A TAIDAI score of 0 was achieved by 21/23 (91%) responders, and TAIDAI remained &gt; 0 for 5/8 (63%) treatment failures. <h3>Conclusion</h3> TAIDAI is a novel disease activity index focused on scoring clinical symptoms only when supported by relevant imaging or laboratory data. TAIDAI should be tested in other cohorts and future clinical trials in TAK. <h3>References</h3> [1]H. Direskeneli et al., Clin Exp Rheumatol 2011 [2]Aydin S. Z. et al, The journal of Rheumatol 2017 [3]Grayson P.C. et al., Arthritis Rheumatol 2018 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.